1. Field of the Invention
The present invention relates generally to index-matching materials used for splicing optical fibers, and in particular relates to index-matching gels suitable for use with nano-engineered optical fibers, and the use of such gels in mechanical splice assemblies and fiber optic connectors.
2. Technical Background
Optical fibers are widely used in a variety of applications, including the telecommunications industry, in which optical fibers are employed in a number of telephony and data transmission applications. Due, at least in part, to the extremely wide bandwidth and the low noise operation provided by optical fibers, the use of optical fibers and the variety of applications in which optical fibers are used are continuing to increase. For example, optical fibers no longer serve merely as a medium for long distance signal transmission, but increasingly are being routed directly to the home or, in some instances, directly to a desk or other work location.
The ever increasing and varied use of optical fibers has spurred the use of fiber optic splice assemblies and connectors. A splice assembly connects one optical fiber to another. Fiber optic connectors are used to terminate the ends of optical fibers and enable faster connection and disconnection than fusion splicing. A typical splice assembly and a typical connector each hold the end of each optical fiber in a ferrule. The ferrule serves to align the respective cores of the two fibers so that light can pass between the ends of the fibers. Certain connectors are formed using splice assemblies.
Splice assemblies and connectors have traditionally generated concern because they introduce loss and because different connector types were typically not compatible. While the use of splice assemblies and connectors was once problematic, manufacturers have taken steps to standardize and simplify them. This increasing user-friendliness has contributed to the increase in the use of fiber optic systems.
To transmit optical signals between two optical fibers efficiently, the splice assembly or connector must not significantly attenuate or alter the transmitted signals. However, while splice assemblies and connectors provide two easy ways to connect two optical fibers (or sets of optical fibers), they also introduce attenuation, which is typically in the range from about 0.05 dB to 0.5 dB. To mitigate attenuation effects in the splice assembly or connector, an index-matching material (typically, a fluid) is often used. The index-matching material is held within the splice assembly or connector so that it presents itself at the interface between the two fiber ends. The index-matching material serves to reduce attenuation due to reflections from the index mismatch at the fiber-fiber interface.
With the advent of so-called nano-engineered optical fibers that have voids at their end face, the use of standard index-matching fluids and gels has become problematic because the fluid or gel tends to migrate or “wick” into the fiber through the voids. An index-matching gel is needed that at most only minimally migrates into the nano-engineered fiber end, while also having robust mechanical properties (and in particular viscoelastic properties) over the range of conditions (e.g., temperature ranges) the gel would typically experience in the field.